Tetrabutylurea

Endpoint summary

Additional information

The acute toxicity of tetrabutyl urea to Danio rerio was investigated in a study conducted according to OECD Guideline 203 (Fish, Acute Toxicity Test; 1992). In this semi-static test, 7 fish per concentration were exposed to nominal concentrations of 0, 0.269, 0.538, 1.075, 2.15, and 4.30 mg TBU/L for 96 h. The concentrations of tetrabutylurea in the test media were assessed by chemical analyses (LC/MS/MS). Analysis of test media revealed tetrabutyl urea concentrations between 60.3 and 92.2% of nominal. Therefore, the geometric mean for each test concentration was calculated resulting in actual concentrations of 0.172, 0.365, 1.0, 1.75 and 2.59 mg/L. The 96 h LC50 was determined to be 1.7 mg/L and 1.4 mg/L based on the nominal and geometric mean measured concentrations, respectively.

The acute toxicity of tetrabutyl urea to Daphnia magna was investigated in a study conducted according to OECD Guideline 202 (Daphnia sp. Acute Immobilisation Test; 2004). In this static test, 20 daphnids per concentration were exposed to nominal concentrations of 0, 0.269, 0.538, 1.075, 2.15, and 4.30 mg TBU/L for 48 h. The concentrations of tetrabutylurea in the test media were assessed by chemical analyses (LC/MS/MS). As the recovered tetrabutyl urea concentrations exceeded the 20 % range at the beginning of the test and decreased more than 20 % from the initial values during the test, the geometric mean for each test concentration was calculated. The 48 h EC50 was determined to be 1.7 mg/L and 1.85 mg/L based on the nominal and geometric mean measured concentrations, respectively.

The toxicity of tetrabutyl urea to the unicellular, green alga Pseudokirchneriella subcapitata was investigated in a study conducted according to OECD Guideline 201 (Alga, Growth Inhibition Test; 2011). In this static test, exponentially growing cultures of the alga were exposed tonominal tetrabutyl urea concentrations of 0 (control), 0.269, 0.538, 1.075, 2.15, and 4.3 mg/L for 72 h. The concentration of tetrabutyl urea was assessed by chemical analysis (LC-MS/MS). As the measured tetrabutyl urea concentrations were outside of the ± 20 % range of the measured initial concentrations for some treatment levels at the end of the study, the geometric mean measured concentrations for each test concentration was calculated. After 72 h of exposure, NOEC values of 0.14 mg/L and 0.58 mg/L were determined for yield and growth rate inhibition, respectively. The 72 h EC50 for yield was determined to be 1.11 mg/L. Since the growth rate inhibition was below 50 % compared to controls at the highest test concentration the 72 h EC50 value was determined to be higher as the highest test concentration (72 h EC50 > 2.95 mg/L; all effect concentrations based on geometric mean measured concentrations).

In a study conducted according to OECD Guideline 209, the respiration inhibition (total respiration, heterotrophic respiration, and respiration due to nitrification) of tetrabutyl urea to activated sludge was found to be low (NOEC>=500 mg/L, LOEC>=1000 mg/L, and EC50>1000 mg/L).